Remove the remaining parts of background idle notification.

BUG=chromium:490559
LOG=NO

Review URL: https://codereview.chromium.org/1425143002

Cr-Commit-Position: refs/heads/master@{#31672}

src/heap/heap.cc

@@ -4210,18 +4210,6 @@ void Heap::IdleNotificationEpilogue(GCIdleTimeAction action,
 }
 
 
-void Heap::CheckBackgroundIdleNotification(double idle_time_in_ms,
-                                           double now_ms) {
-  // TODO(ulan): Remove this function once Chrome uses new API
-  // for foreground/background notification.
-  if (idle_time_in_ms >= GCIdleTimeHandler::kMinBackgroundIdleTime) {
-    optimize_for_memory_usage_ = true;
-  } else {
-    optimize_for_memory_usage_ = false;
-  }
-}
-
-
 double Heap::MonotonicallyIncreasingTimeInMs() {
   return V8::GetCurrentPlatform()->MonotonicallyIncreasingTime() *
          static_cast<double>(base::Time::kMillisecondsPerSecond);
@@ -4246,8 +4234,6 @@ bool Heap::IdleNotification(double deadline_in_seconds) {
   double start_ms = MonotonicallyIncreasingTimeInMs();
   double idle_time_in_ms = deadline_in_ms - start_ms;
 
-  CheckBackgroundIdleNotification(idle_time_in_ms, start_ms);
-
   tracer()->SampleAllocation(start_ms, NewSpaceAllocationCounter(),
                              OldGenerationAllocationCounter());
 

src/heap/heap.h

@@ -1801,7 +1801,6 @@ class Heap {
   void IdleNotificationEpilogue(GCIdleTimeAction action,
                                 GCIdleTimeHeapState heap_state, double start_ms,
                                 double deadline_in_ms);
-  void CheckBackgroundIdleNotification(double idle_time_in_ms, double now_ms);
 
   inline void UpdateAllocationsHash(HeapObject* object);
   inline void UpdateAllocationsHash(uint32_t value);